Abstract
This study was intended to examine the influence of the addition of slaked lime on electrical conductivity (EC) and the mineral extraction rate of swine manure compost. Results showed that the larger the slaked lime addition rate was, the lower the EC tended to become. Four weeks after slaked lime addition and at the end of aeration, the larger the slaked lime addition rate was, the lower the concentrations of minerals in the manure extract in distilled water became, except for the calcium concentration, which did not differ regardless of the addition rate. Extraction rates of phosphorus, calcium, magnesium, potassium, and sodium decreased according to the addition of slaked lime ; especially those of phosphorus and magnesium decreased sharply. The increase of exchangeable potassium and sodium can explain the decrease of their extraction rates in water by slaked lime addition. As for the manure extract in 0.3N HCl after the four-week period, the more slaked lime was added, the higher the calcium concentration became. Conversely, concentrations of phosphorus, magnesium, potassium, and sodium decreased as more slaked lime was added. Irrespective of the slaked lime addition rate, extraction rates of phosphorus, calcium, potassium, and sodium were approximately over 90%. Nevertheless, the magnesium concentration decreased more along with the increase of the slaked lime addition rate. Generation of magnesium ammonium phosphate could not explain the sharply decreased extraction rates of phosphorus and magnesium that resulted from slaked lime addition.
